< could only see committed rows from another transaction. However,
> could only see rows from another completed transaction. However,
981c981
< proper visibility of the row, for example, for cursors.
> proper visibility of the row's cmin, for example, for cursors.
on a page, as suggested by ITAGAKI Takahiro. Also, change a few places
that were using some other estimates of max-items-per-page to consistently
use MaxOffsetNumber. This is conservatively large --- we could have used
the new MaxHeapTuplesPerPage macro, or a similar one for index tuples ---
but those places are simply declaring a fixed-size buffer and assuming it
will work, rather than actively testing for overrun. It seems safer to
size these buffers in a way that can't overflow even if the page is
corrupt.
* Merge xmin/xmax/cmin/cmax back into three header fields
Before subtransactions, there used to be only three fields needed to
store these four values. This was possible because only the current
transaction looks at the cmin/cmax values. If the current transaction
created and expired the row the fields stored where xmin (same as
xmax), cmin, cmax, and if the transaction was expiring a row from a
another transaction, the fields stored were xmin (cmin was not
needed), xmax, and cmax. Such a system worked because a transaction
could only see committed rows from another transaction. However,
subtransactions can see rows from outer transactions, and once the
subtransaction completes, the outer transaction continues, requiring
the storage of all four fields. With subtransactions, an outer
transaction can create a row, a subtransaction expire it, and when the
subtransaction completes, the outer transaction still has to have
proper visibility of the row, for example, for cursors.
One possible solution is to create a phantom cid which represents a
cmin/cmax pair and is stored in local memory.
< * Maintain a map of recently-expired rows
<
< This allows vacuum to target specific pages for possible free space
< without requiring a sequential scan.
<
Update entry:
> One complexity is that index entries still have to be vacuumed, and
> doing this without an index scan (by using the heap values to find the
> index entry) might be slow and unreliable, especially for user-defined
> index functions.
saves nearly 700kB in the default shared memory segment size, which seems
worthwhile, and it is a feature that many users won't use anyway. Per
Heikki's argument, there is no point in a compromise value --- those who
are using 2PC at all will probably want it at least equal to max_connections.
But we can't set it to zero by default without breaking the prepared_xacts
regression test.
so that the latter estimates the number of groups that grouping will
produce. This is needed because it is primarily query_planner that
makes the decision between fast-start and fast-finish plans, and in the
original coding it was unable to make more than a crude rule-of-thumb
choice when the query involved grouping. This revision helps us make
saner choices for queries like SELECT ... GROUP BY ... LIMIT, as in a
recent example from Mark Kirkwood. Also move the responsibility for
canonicalizing sort_pathkeys and group_pathkeys into query_planner;
this information has to be available anyway to support the first change,
and doing it this way lets us get rid of compare_noncanonical_pathkeys
entirely.
to copy the whole plan tree before invoking adjust_plan_varnos(); else
if there is any multiply-linked substructure, the latter might increment
some Var's varno twice. Previously there were some retail copyObject
calls inside adjust_plan_varnos, but it seems a lot safer to just dup the
whole tree first. Also, set_inner_join_references was trying to avoid
work by not recursing if a BitmapHeapScan's bitmapqualorig contained no
outer references; which was OK at the time the code was written, I think,
but now that create_bitmap_scan_plan removes duplicate clauses from
bitmapqualorig it is possible for that field to be NULL while outer
references still remain in the qpqual and/or contained indexscan nodes.
For safety, always recurse even if the BitmapHeapScan looks to be outer
reference free. Per reports from Michael Fuhr and Oleg Bartunov.
>
> Another issue is whether underlying table changes should be reflected
> in the view, e.g. should SELECT * show additional columns if they
> are added after the view is created.
> o Issue a warning if a change-on-restart-only postgresql.conf value
> is modified and the server config files are reloaded
> o Mark change-on-restart-only values in postgresql.conf
205a209
> o Fix SELECT '0.01 years'::interval, '0.01 months'::interval
>
> Currently, while \e saves a single query as one entry, interactive
> queries are saved one line at a time. Ideally all queries
> whould be saved like \e does.
>
> o Allow multi-line column values to align in the proper columns
>
> If the second output column value is 'a\nb', the 'b' should appear
> in the second display column, rather than the first column as it
> does now.
< in PL/PgSQL is to use EXECUTE.
> in PL/PgSQL is to use EXECUTE. One complexity is that a function
> might itself drop and recreate dependent tables, causing it to
> invalidate its own query plan.
< inheritance, and allow it to work for UPDATE and DELETE queries
> inheritance, allow it to work for UPDATE and DELETE queries, and allow
> it to be used for all queries with little performance impact
< * Allow constraint_elimination to be automatically performed
<
< This requires additional code to reduce the performance loss caused by
< constraint elimination.
< * -Allow limits on per-db/role connections
43d41
< * -Prevent dropping user that still owns objects, or auto-drop the objects
49d46
< * -Add the client IP address and port to pg_stat_activity
< * -Add session start time and last statement time to pg_stat_activity
< * -Add a function that returns the start time of the postmaster
230d224
< o -Allow MIN()/MAX() on arrays
< o -Modify array literal representation to handle array index lower bound
< of other than one
253d244
< * -Add function to return compressed length of TOAST data values
< * -Prevent to_char() on interval from returning meaningless values
<
< For example, to_char('1 month', 'mon') is meaningless. Basically,
< most date-related parameters to to_char() are meaningless for
< intervals because interval is not anchored to a date.
<
< * -Have views on temporary tables exist in the temporary namespace
< * -Allow temporary views on non-temporary tables
329d311
< * -Add BETWEEN SYMMETRIC/ASYMMETRIC
< * -Add E'' escape string marker so eventually ordinary strings can treat
< backslashes literally, for portability
<
< * -Allow additional tables to be specified in DELETE for joins
<
< UPDATE already allows this (UPDATE...FROM) but we need similar
< functionality in DELETE. It's been agreed that the keyword should
< be USING, to avoid anything as confusing as DELETE FROM a FROM b.
<
341d313
< * -Allow REINDEX to rebuild all database indexes
< * -Add an option to automatically use savepoints for each statement in a
< multi-statement transaction.
<
< When enabled, this would allow errors in multi-statement transactions
< to be automatically ignored.
<
426d391
< o -Allow FOR UPDATE queries to do NOWAIT locks
473d437
< o -Allow COPY to understand \x as a hex byte
< o -Allow COPY to optionally include column headings in the first line
< o -Allow COPY FROM ... CSV to interpret newlines and carriage
< returns in data
525d485
< o -Have SHOW ALL show descriptions for server-side variables
< o -Allow PL/PgSQL's RAISE function to take expressions
<
< Currently only constants are supported.
<
< o -Change PL/PgSQL to use palloc() instead of malloc()
545d499
< o -Allow PL/pgSQL EXECUTE query_var INTO record_var;
550d503
< o -Pass arrays natively instead of as text between plperl and postgres
598d550
< o -Add dumping and restoring of LOB comments
638d589
< * -Implement shared row locks and use them in RI triggers
642d592
< * -Allow triggers to be disabled
< * -Add two-phase commit
<
<
< * -Prevent inherited tables from expanding temporary subtables of other
< sessions
< * -Use indexes for MIN() and MAX()
<
< MIN/MAX queries can already be rewritten as SELECT col FROM tab ORDER
< BY col {DESC} LIMIT 1. Completing this item involves doing this
< transformation automatically.
<
< * -Use index to restrict rows returned by multi-key index when used with
< non-consecutive keys to reduce heap accesses
<
< For an index on col1,col2,col3, and a WHERE clause of col1 = 5 and
< col3 = 9, spin though the index checking for col1 and col3 matches,
< rather than just col1; also called skip-scanning.
<
< * -Fetch heap pages matching index entries in sequential order
<
< Rather than randomly accessing heap pages based on index entries, mark
< heap pages needing access in a bitmap and do the lookups in sequential
< order. Another method would be to sort heap ctids matching the index
< before accessing the heap rows.
<
< * -Allow non-bitmap indexes to be combined by creating bitmaps in memory
<
< This feature allows separate indexes to be ANDed or ORed together. This
< is particularly useful for data warehousing applications that need to
< query the database in an many permutations. This feature scans an index
< and creates an in-memory bitmap, and allows that bitmap to be combined
< with other bitmap created in a similar way. The bitmap can either index
< all TIDs, or be lossy, meaning it records just page numbers and each
< page tuple has to be checked for validity in a separate pass.
<
< * -Fix incorrect rtree results due to wrong assumptions about "over"
< operator semantics
782d694
< o -Add concurrency to GIST
813d724
< * -Allow multiple blocks to be written to WAL with one write()
< * -Consider use of open/fcntl(O_DIRECT) to minimize OS caching,
< for WAL writes
<
< O_DIRECT doesn't have the same media write guarantees as fsync, so it
< is in addition to the fsync method, not in place of it.
<
< * -Cache last known per-tuple offsets to speed long tuple access
< * -Allow the size of the buffer cache used by temporary objects to be
< specified as a GUC variable
<
< Larger local buffer cache sizes requires more efficient handling of
< local cache lookups.
<
< * -Improve the background writer
<
< Allow the background writer to more efficiently write dirty buffers
< from the end of the LRU cache and use a clock sweep algorithm to
< write other dirty buffers to reduced checkpoint I/O
<
897d788
< * -Add a warning when the free space map is too small
917d807
< o -Move into the backend code
< * -Make locking of shared data structures more fine-grained
<
< This requires that more locks be acquired but this would reduce lock
< contention, improving concurrency.
<
< * -Improve SMP performance on i386 machines
<
< i386-based SMP machines can generate excessive context switching
< caused by lock failure in high concurrency situations. This may be
< caused by CPU cache line invalidation inefficiencies.
<
979d857
< o -Add ability to turn off full page writes
< * -Eliminate WAL logging for CREATE TABLE AS when not doing WAL archiving
< * -Change WAL to use 32-bit CRC, for performance reasons
<
< * -Use CHECK constraints to influence optimizer decisions
<
< CHECK constraints contain information about the distribution of values
< within the table. This is also useful for implementing subtables where
< a tables content is distributed across several subtables.
<
1045d913
< * -ANALYZE should record a pg_statistic entry for an all-NULL column
1099d966
< * -Remove kerberos4 from source tree
1103d969
< * -Make src/port/snprintf.c thread-safe
1118d983
< * -Add C code on Unix to copy directories for use in creating new databases
1133d997
< o -Improve dlerror() reporting string
